21020530 has 16 divisors (see below), whose sum is σ = 37934424. Its totient is φ = 8386560.

The previous prime is 21020521. The next prime is 21020533. The reversal of 21020530 is 3502012.

It can be written as a sum of positive squares in 4 ways, for example, as 8139609 + 12880921 = 2853^2 + 3589^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21020530.

It is not an unprimeable number, because it can be changed into a prime (21020533) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1714 + ... + 6706.

Almost surely, 2^21020530 is an apocalyptic number.

21020530 is a deficient number, since it is larger than the sum of its proper divisors (16913894).

21020530 is a wasteful number, since it uses less digits than its factorization.

21020530 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5421.

The product of its (nonzero) digits is 60, while the sum is 13.

The square root of 21020530 is about 4584.8151543983. The cubic root of 21020530 is about 275.9822942503.

Adding to 21020530 its reverse (3502012), we get a palindrome (24522542).

The spelling of 21020530 in words is "twenty-one million, twenty thousand, five hundred thirty".